Human chorionic gonadotropin is a glycoprotein hormone of placental origin. The proposed research program is concerned with a detailed study of its chemistry and biological properties. More specifically, problems such as the elucidation of the complete primary structure, microheterogeneity, structure and activity relationship, and comparative studies on hCG from different species will be investigated. The studies on the structure of hCG will involve the determination of the number and size of the carbohydrate units, the order of monosaccharides in the units and the mode of attachment of the sugars to one another and mode of attachment of the complete unit to polypeptide chain. With the knowledge of the amino acid sequence of hCG, the studies on the structure activity relationship will be undertaken. Specific enzymatic and chemical modification of hCG will be carried out and the modified forms will be evaluated for various biological properties. These studies will then enable us to investigate disease state hCG from choriocarcinoma and other related diseases.